1. Field of the Invention
The present invention relates to an information terminal having a communication function, such as a mobile telephone and personal digital assistant (PDA), and, more particularly, to an information terminal having a function of acquiring content from an information site and storing/playing it back, and a content storage/playback method.
2. Description of the Related Art
In recent years, streaming services that allow users to download rich content such as music from content servers to information terminals have begun to prevail. In the information terminal that utilizes such services, the downloaded content is temporarily stored in memory, and the stored content is read out from memory and played back in accordance with a user's playback operation. Some content is assigned a usage rule indicating the use condition. The usage rule includes a stateless usage rule that does not require management of a variable state, i.e., one that designates a playback validity period, and a stateful usage rule that requires management of a variable state, i.e., one that designates a playback count.
On the other hand, it is proposed to use a hard disk (HDD) as a memory used to store content. When the hard disk is used as the memory, a large amount of content can be stored with lower cost than with use of a flash memory or the like. However, the hard disk is generally vulnerable to shock and easily breaks.
Hence, content stored in the hard disk is backed up to an external storage device. Desirably, one can restore backup files of the content from the external storage device to the hard disk when the content cannot be used due to a problem with the hard disk or the like.
For example, in a known method, when the content server downloads content with the use condition to the information terminal, it appends the network address of a backup server to the content to be downloaded. The information terminal transmits the content to the backup server based on the network address upon backing up the downloaded content. The backup server saves the transmitted content in correspondence with the telephone number of the communication terminal as the transmission source. However, this method requires a dedicated backup server, and equipment investment of the content seller or use condition manager is required accordingly. Note that the technique that uses the backup server is described in detail in Jpn. Pat. Appln. KOKAI Publication No. 2004-48180.
Also, a technique for backing up content stored in a mobile telephone or mobile terminal such as a PDA or the like using a personal computer has been proposed. For example, content stored in a hard disk of a mobile terminal is encrypted together with its usage rule, and the encrypted content including the usage rule is copied to the personal computer intact. When the content is deleted due to a problem with the hard disk or the like, the encrypted content including the usage rule is restored from the personal computer to the hard disk.
However, with the above technique, when the usage rule included in the content is the stateful usage rule, the remaining playback count managed by the mobile terminal does not match that backed up by the personal computer. For this reason, when the backup content is restored to the hard disk, the stateful usage rule cannot be accurately managed.